Method for making cellular structures

ABSTRACT

A method for making a cellular structure having a plurality of walls extending along intersecting planes and together providing abutting cells, such walls being connected at their locations of intersection by cruciform sections and formed by flexing portions of a slit web material into planes disposed at angles to the plane of the original web material.

United States Patent Inventor Theodore H. Fairbanks West Chester, Pa.

Appl. No. 714,231

Filed Mar. 19,1968

Patented Oct. 26, 1971 Assignee FMC Corporation Philadelphia, Pa.

METHOD FOR MAKING CELLULAR STRUCTURES 5 Claims, 9 Drawing Figs.

US. Cl 156/257, 161/68,161/110 Int. Cl 1332b 3/10 Field of Search 161/110, 111,113, 68; 52/181, 443; 229/29 F; 156/205, 292, 256, 253

[56] References Cited UNITED STATES PATENTS 1,433,232 10/1922 Rogers52/443 2,261,307 11/1941 Still l i 161/110 2,481,046 9/1949 Schurlock161/110 3,011,602 12/1961 Ensrudetal 161/110 3,018,209 1/1962Dijksterhuis et a1. 156/256 3,137,893 6/1964 Gelpke 156/253 3,479,24011/1969 Moser 156/205 Primary Examiner-Samuel Feinberg AssistantExaminer-David Bent Au0rneysThomas R. O'Malley, George F. Mueller andEugene G. Horsky ABSTRACT: A method for making a cellular structurehaving a plurality of walls extending along intersecting planes andtogether providing abutting cells, such walls being connected at theirlocations of intersection by cruciform sections and formed by flexingportions of a slit web material into planes disposed at angles to theplane ofthe original web material.

METHOD FOR MAKING CELLULAR STRUCTURES The invention relates to a methodfor making articles of cellular construction.

Members of cellular, and more particularly of honeycomb construction,are light in weight and provide substantial structural volume, rigidityand strength for the relatively small amount of material used in theirconstruction. Such honeycomb members have, therefore, found wideapplication in many fields, as for example, load-bearing floors,ceilings, and walls; as reinforcing cores or panels in flush doors; asrigid article separators or spacers; as grilles or screens for suspendedceilings and light fixtures; etc.

Honeycomb structures can be manufactured by a variety of known methods.Perhaps one of the most common methods involves interlocking of slottedstrips or slats in crossing rela tionship. In another known procedure,strips of suitable material are bent, with sharp corners, into acorrugated form and then connected to each other in side-by-siderelationship to provide a series of abutting cells. These and otherknown methods for making honeycomb structures often require expensivematerials, generally involve a number of machining steps and/ormanipulations of the different members during assembly and are usuallynot suited for rapid manufacture of continuous cellular or honeycombstructures. Accordingly, a primary object of this invention is toprovide a generally new or improved and more satisfactory method formaking cellular or honeycomb structures.

Another object is the provision of an improved method for making ahoneycomb structure which is light in weight, possess gOOd structuralvolume, rigidity and strength and can be made from inexpensive materialsand with low manufacturing COSIS.

A further object is to provide an improved method for making a honeycombstructure from a continuous traveling web material.

A still further object is the provision of an improved method for makingcontinuous honeycomb structures rapidly and at low costs.

These and other objects are accomplished in accordance with the presentinvention by a method in which a pliable web material is slit along onlya portion of the length of each of a series of lines defining aplurality of abutting parallelograms, with adjacent parallelogramsabutting along a common line. Slits of the individual parallelogramsmeeting or intersecting at only one pair of diagonally opposed cornersthereof and terminating short of their other pair of diagonally opposedcorners. Thus, ends of such slits are separated by narrow neck sectionsof web material. Each of the portions of the web material extendingbetween these neck sections is then pivoted as a planar unit by flexingor twisting the web material in the areas of the neck sections into ahelical configuration. The free corners of the individualparallelograms; that is, the diagonally opposed corners thereof at whichthe slits meet, are thus moved in opposite directions away from theplane of the original web material.

As noted above, the web material must be pliable to permit the necksections thereof to be flexed or twisted into helical shapes withouttearing. A variety of web materials may be employed in making thecellular structures by the method of the present invention, includingmaterials which are thermoplastic, such as polyamides orsuperpolyamides, polyesters, polyvinyl chlorides, and copolymersthereof, polyolefins, and cellulose acetates; thermosetting materials;metals, such as aluminum, copper, brass, sheet steel; papers; fabrics;and etc.

With the exception of the web materials formed of ductile metals, it isgenerally necessary to set the pivoted portions of the web material tofix the same in position. Thus, with web materials which are ofthermoplastic character, the portions of the web material which extendbetween the neck sections may be in a heat-softened condition whilebeing pivoted and then cooled to set the same in fixed positions.Thermosetting web material may, of course, be set by heat, whilematerials such as paper or fabrics may be fixed by the application ofcoatings capable of being hardened or otherwise stabilized.

The slits formed in the web material must together define a plurality ofabutting parallelograms; that is, with adjacent parallelograms abuttingalong a common slit. The lengths of the neck sections of web materialbetween the ends of the slits must be such as to permit the same toeasily flex or twist as the portions of the web material extendingbetween such neck sections are pivoted as planar units. The lengths ofthese neck sections of web material will depend, to some degree. uponthe particular characteristics of the web material employed.

In honeycomb structures intended primarily for decorative applications,such as screens or grilles, the slits formed in the web material may besuch as to define parallelograms of different sizes. if further desired,the portions of the web material extending between the neck sectionsthereof may be pivoted, as planar units, to different degrees relativeto the original plane of the web material.

Honeycomb structures which possess substantial strength and rigidity areformed by initially providing a web with slits which are of equallength, and preferably extend at right angles to each other. Theportions of the web material extending between the neck sections thereofare then pivoted. as planar units, through an angle of from the originalplane of web material and, if necessary, set in such positions.

The cellular or honeycomb structure produced by the above-describedmethod includes a series of walls extending along each of a plurality ofplanes which intersect with each other, with sections of cruciformconfiguration integrally connecting the walls to each other at thelocations of intersection of their respective planes. These cruciformsections each have a central portion, disposed in a plane extending atan angle to the planes of the series of walls, and legs of helical shapeextending between the central portion of the cruciform section and thewalls adjacent thereto. Desirably, the central portions of the cruciformsections are disposed in a planewhich is substantially perpendicular tothe planes of the series of walls, and the walls themselves arepreferably located along planes which intersect at substantially rightangles with each other.

Structures of still greater strength and rigidity than those heretoforedescribed are provided by attaching a continuous sheet, web material orother flat member to at least one and preferably both sides of thehoneycomb structure to thereby form a composite product. Attachment ofsuch continuous sheets may be effected by projecting the free corners ofthe pivoted portions of the web material through suitable slots formedin the sheets themselves. These projecting corners are then distorted,as by bending, twisting, or are heat softened to lock the sheets inplace.

An alternative procedure for making a composite product using thehoneycomb structure as a core entails removing the free corners of theportions of the web material supported between the neck sections priorto pivoting of such portions. Such free corners may be removed bycutting the same along lines extending generally perpendicular to a lineextending between such free corners. The edges thus provided will extendgenerally parallel to the original plane of the web material after theportions of the web material extending between the neck sections arepivoted into planes substantially perpendicular to their originalplanes. A continuous sheet, web material or other flat member is thenfixed to these edges of the pivoted portions of the web material. as byadhesives, heat. etc.

In the composite products described, it will be apparent that the sheetsfixed to the honeycomb structure maintain the pivoted portions thereofin the fixed positions. Moreover, such attached sheets serve also todistribute loads over a large area of the composite product and, ifdesired, may be made fluidtight to impart buoyant and perhapsheat-insulating characteristics to such products.

The continuous sheets or other flat members of the composite productsdescribed above may formed of any desired materials and may be the sameor different from that of the honeycomb structure itself. Such sheetsmay include various additives, such as colorants, stabilizers, etc., ifdesired or necessary and, in the case of plastic materials, may be oftransparent or translucent character.

The apparatus employed in the method of the present invention includesmeans for providing a pliable web material with closely spaced rows ofcrosscuts in which the crosscuts of alternate rows are located betweenthe ends of crosscuts in the rows adjacent thereto, a first and secondseries of pyramidshaped projections for engaging with opposite sides ofthe web material, respectively, at the locations of the crosscuts, withthe projections of two series thereof being in staggered relationship,and means for moving the first and second series of projections towardeach other and through the web material to thereby deflect portionsthereof from their original plane. Preferably, the apparatus is designedfor continuous manufacture of honeycomb structures. Thus, the means forcutting the web material as well as the two, series of projections arecarried by suitable rollers or belt conveyors so as to permit the sameto perform their intended operations on a web material concomitantlywith its continuous travel.

To facilitate the manufacture of composite products of the character asheretofore described, the apparatus also includes, in one embodiment,means for providing a continuous sheet with slits at spaced locationscorresponding with the spacing of the deflected portions of the webmaterial, means for disposing the slit sheet onto the deflected portionsof the web material so that such portions project partially through theslit sheet, and means for distorting the projecting parts of thedeflected portions of the web material to thus lock the sheet in place.

In another embodiment of the apparatus means are included for cuttingthe web along lines extending between adjacent slits of each of thecrosscuts, to thereby remove a rectangular section of web materialtherefrom, and means positioned beyond the series of projections forattaching a continuous sheet to the outermost edges of the deflectedportions of the web material.

In the drawing,

FIG. I is a diagrammatic side view of the apparatus of the presentinvention;

FIG. 2 is a plan view of a portion of web material following a slittingstage of the method of the present invention;

FIG. 3 is a fragmentary plan view of a portion of the apparatus shown inFIG. 1;

FIG. 4 is a view similar to FIG. 1 showing a portion of the apparatus onan enlarged scale and illustrating another stage of the method of thepresent invention;

FIG. 5 is a plan view of a portion of the honeycomb structure providedby the method ofthe present invention;

FIG. 6 illustrates the cellular or honeycomb structure provided by themethod of the present invention employed as a core of composite product;

FIG. 7 is a view similar to FIG. 5 showing a composite product ofmodified construction;

. FIGS. 8 and 9 are views similar to FIG. 2 showing web materials withmodified arrangements of slits.

With reference to FIG. 1 of the drawing reference character indicates acontinuous web material and particularly a thermoplastic film, such asof polyethylene, which is drawn from a suitable source and shaped into acellular or honeycomb structure as it is continuously advanced throughthe apparatus which is illustrated. Upon entry into the apparatus, thefilm 15 passes between a cutter roll 17 and a backup roll 19 whichtogether provide the film with rows of crosscuts 21. As shown in FIG. 2,the crosscuts 21 in alternate of such rows are located between the endsof the crosscuts 21 in the rows which are adjacent thereto.

The crosscuts 21 each consist of four individual slits 23, 25, 27 and29. These individual slits of the different crosscuts 21 extend alongonly a portion of the length of each of a series of lines which togetherdefine a series of abutting parallelograms or square portions 31. Ineach of these square portions 31, the slits forming the same meet orintersect at only one pair of opposed corners thereof. At the other pairof such opposed corners thereof, the individual slits terminate justshort of each and are separated at their ends by narrow neck sections33.

If desired, a square segment 35 of the film 15 is removed from thecenter of each of the crosscuts 21, preferably simultaneously with theformation of such crosscuts. The edges 37 provided by the removal ofthese square film segments 35 extend substantially perpendicular tolines drawn between opposed corners of the square portions 31 and afterfilm shaping, as hereafter described, will be in planes which areparallel to the original plane of the film.

Upon the movement of the film l5 beyond the rolls 17 and 19 it isimpinged along its opposite sides by hot gases delivered by nozzles 39,and then advanced in between a pair of endless belts 41 and 43, both ofwhich include a series of truncated, pyramid-shaped projections 45. Thehot gases which are discharged from the nozzles 39 are not intended tomelt or cause undesired flow of the film material but merely soften thesame.

The endless belt 41 is laced over drums 47 and 49, at least one of whichis driven in the direction of arrow 51. The belt 43 is likewise lacedover drums 53 and 55, at least one of which is driven in the directionof arrow 57. Between the reaches of the respective belts 41 and 43 aredisposed nozzles 59 for directing cool air against the opposing beltreaches and the portion of the film therebetween. For purposes asdescribed hereafter. the reaches of the belt 43 are longer than that ofthe belt 41 and thus its uppermost reach is supported against sagging bya fixed table 60.

As shown in FIG. 3, the projections 45 of the belt 43 are positioned toengage with one side of the film 15 at the locations of the crosscuts 21in alternate longitudinally extending rows thereof. Further, it will benoted that the projections 45 ofthe belt 43 are each disposed so thatthe corners thereof will be aligned with the slits of the crosscuts.

As each of these projections 45 of the belt 43 move into engagement withone side of the film 15, four of the portions 31 are simultaneouslypivoted as planar units about their respective neck sections 33 and areurged toward positions as shown in FIG. 4. The projections 45 of thebelt 41 are intended to engage the opposite side of the film 15, butonly at the locations of crosscuts 21 which are not engaged byprojections 45 of the belt 43. Thus, the projections 45 of both belts 41and 43 together cooperate in pivoting the film portions 31 and inmaintaining the same in vertical planes, as shown in FIG. 4, as they areadvanced relative to the nozzles 59 where they are cooled and set inplace.

The cellular or honeycomb structure 61 which is produced may be thenremoved from between the belts 41 and 43. In such structure, as shown inFIG. 5, the portions 31 of the original film 15 extend along planeswhich intersect each other at substantially right angles. Between suchportions 31 are cruciform sections 63, each of which includes a centralportion 65 and legs 67 of helical configuration. The central portions 65of the cruciform sections all lie in a plane which is substantiallyperpendicular to the planes of the portions 31. The helical shaped legs67 are, in effect, the film neck sections 33 after they have beentwisted during the pivoting of the portions 31.

In lieu of removing the honeycomb structure 61 from the apparatus,continuous sheets or films 69 may be attached to one and preferably toopposite sides thereof to provide a composite product 71 as shown inFIG. 6. As heretofore mentioned, square segments 35 of the film 15 neednot be removed and in such instance the free corners of the filmportions 31 will appear in the resulting honeycomb structure 61 atlocations between the cruciform sections 63. The films 69 may thereforebe slit at 73 to receive the corners of the portions 31 of the structure61 and then be bent over as shown at 75 to lock the films 69 in place.

On the other hand, with removal of the square film segments 35, the film69 may be attached to the edges 37 of the portions 31 of the resultinghoneycomb structure 61 to provide a composite product 77 as shown inFIG. 7. More particularly, and as shown in FIG. 1, a film 69 may beguided about a roller 79 and laid onto the uppermost surface of thehoneycomb structure 61. As such honeycomb structure 61 and film 69 aretogether carried continuously by the upper reach of the belt 43, thefilm 69 is softened by a heater 81 and then cooled by air from a nozzle83 and thereby bonded in place.

A film 69 may be bonded to the underside of the honeycomb structure 61in a like manner after such structure moves beyond the belt 43. As shownin FIG. 1, this film 69 is guided by roller 85 against the underside ofthe honeycomb structure 61, softened and pressed by a heater 87 and thencooled as by air from a nozzle 89. A backup plate is provided oppositelyof the heater 87 to prevent upward movement of the composite structurein this area.

ln making the honeycomb structure 61, the slits 23, 25, 27 and 29 of thecroscuts 21 formed film are of substantially the same length and extendalong planes which intersect at substantially right angles with eachother. While the honeycomb structure which is provided, as shown in FIG.5, is of a preferred construction, the method of the present inventionis also applicable to making honeycomb structures having different cellarrangements. Thus, as illustrated in FIG. 8, a film 91 may be providedwith crosscuts 93 in which the slits thereof extend along planes whichintersect at angles other than right angles. A further alternative isshown in FIG. 9 wherein a film 95 is provided with crosscuts 97, each ofwhich includes slits 99, t0! and 103 which are of like size and shorterthan the slit 105. The slit film 91 and 95 shown in FIGS. 8 and 9,respectively are shaped into honeycomb structures in the same manner asheretofore described.

It is to be understood that changes and variations may be made withoutdeparting from the spirit and scope of the present invention as definedin the appended claims.

' lclaim:

1. A method of making a cellular structure including the steps ofslitting a pliable web material along only a portion of the length ofeach of a series of lines defining a plurality of abuttingparallelograms with adjacent parallelograms abutting along a commonline, the slits of each such parallelogram intersecting at only one pairof diagonally opposed corners thereof and terminating short of the otherpair of diagonally opposed corners thereof so that the ends of suchslits are separated by narrow neck sections of web material which arecapable of flexing, and pivoting each of the portions of the webmaterial extending between said neck sections as a planar unit at anangle to its original plane by flexing the web material in the areas ofthe neck sections into a helical configuration.

2. Method as defined in claim I wherein the portions of the web materialextending between said neck sections are each pivoted as a planar unitthrough an angle of 3. A method as defined in claim 2 wherein the slitsforming adjacent sides of each parallelogram extend at right angles toeach other.

4. A method as defined in claim 2 further including the step ofdisposing a continuous sheet onto one side of the cellular structure,projecting only a part of the free corners of the pivoted portions ofthe web material through said sheet, and distorting said projectingparts of the pivoted portions of the web material to lock said sheet inplace.

5. A method as defined in claim 2 further including the step of removingthe free comers of the portion of the web material supported by saidneck sections prior to pivoting of the same, said free corners beingremoved by cutting such portions along lines extending substantiallyperpendicular to a line extending between said one pair of opposedcorners of each of the parallelograms whereby the pivoted portions ofthe web are provided with edges which are substantially parallel to theoriginal plane of such portions, and attaching a continuous sheet tosaid edges to provide a laminated product.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.3,616,025 Dated October 26, 1971 Inventor(s) Theodore H. Fairbanks It iscertified that error appears in the above-identified patent and thatsaid Letters Patent are hereby corrected as shown below:

Column 1, line 45, "Slits" should'read The slits Column 3 line 39, after"apparatus" insert employed in the method Jigned and sealed this 13thday of April 1972,

(SDAL Rttestr *mxmm; I-I.FL1JTGE55;R, JR ROBERT TWITTSCHALK AttestlngOfficer Commissioner of Patents

2. Method as defined in claim 1 wherein the portions of the web materialextending between said neck sections are each pivoted as a planar unitthrough an angle of 90*.
 3. A method as defined in claim 2 wherein theslits forming adjacent sides of each parallelogram extend at rightangles to each other.
 4. A method as defined in claim 2 furtherincluding the step of disposing a continuous sheet onto one side of thecellular structure, projecting only a part of the free corners of thepivoted portions of the web material through said sheet, and distortingsaid projecting parts of the pivoted portions of the web material tolock said sheet in place.
 5. A method as defined in claim 2 furtherincluding the step of removing the free corners of the portion of theweb material supported by said neck sections prior to pivoting of thesame, said free corners being removed by cutting such portions alonglines extending substantially perpendicular to a line extending betweensaid one pair of opposed corners of each of the parallelograms wherebythe pivoted portions of the web are provided with edges which aresubstantially parallel to the original plane of such portions, andattaching a continuous sheet to said edges to provide a laminatedproduct.